Your beer will be darker in color and more carmally in taste with the darker grain. To counter that you could run your recipe through any software even the free online software http://beercalculus.hopville.com/recipe and start decreasing the amount of crystal 80 until the SRMs (color) and the gravity matches.

__________________
Like my snazzy new avatar? Get Sons of Zymurgy swag, here, and brew with the best.

Revvy's one of the cool reverends. He has a Harley and a t-shirt that says on the back "If you can read this, the bitch was Raptured. - Madman

I gotta tell ya, just between us girls, that Revvy is HOT. Very tall, gorgeous grey hair and a terrific smile. He's very good looking in person, with a charismatic personality... he drives like a ****ing maniac! - YooperBrew

The difference will be more of a caramel/toffee flavor from the 80. It will still be a good beer, just a darker, and with those flavors added, instead of the much lighter sweetness of the Crystal 10. It depends on how close to Ed's you want your brew to be, but the 80 won't hurt anything either.

If your brew shop has Cara Hell, it would be closer to the 10, though still a little darker (20-30L as opposed to 10).

To figure this out, first type in the original recipe with the 10l and that will tell you the srm and the og of the recipe. Then delete the crystal and switch with the same amount of the 80l...this will show you the change in those variable, then start backing off on the amount until you get as close as you can to the SRms of the original recipe..then if the gravit is drastically under the og of the original recipe, up the extract or the basemalt til you arrive at the og..

__________________
Like my snazzy new avatar? Get Sons of Zymurgy swag, here, and brew with the best.

Revvy's one of the cool reverends. He has a Harley and a t-shirt that says on the back "If you can read this, the bitch was Raptured. - Madman

I gotta tell ya, just between us girls, that Revvy is HOT. Very tall, gorgeous grey hair and a terrific smile. He's very good looking in person, with a charismatic personality... he drives like a ****ing maniac! - YooperBrew

even though the color will be the same with decreasing, how about the flavor?

It will be close in flavor when you back it off. You will find out that you will be using significanlty less of the darker malt, this when diluted with the rest of the recipe will make it pretty close.

This is how you learn to come up with your own recipes....

__________________
Like my snazzy new avatar? Get Sons of Zymurgy swag, here, and brew with the best.

Revvy's one of the cool reverends. He has a Harley and a t-shirt that says on the back "If you can read this, the bitch was Raptured. - Madman

I gotta tell ya, just between us girls, that Revvy is HOT. Very tall, gorgeous grey hair and a terrific smile. He's very good looking in person, with a charismatic personality... he drives like a ****ing maniac! - YooperBrew

For example if your original recipe was 5 pounds of Bries amber extract and 3 pounds of crystal 10L that would produce a beer with a starting grravity of 1.051 and 10 srms.

To match those numbers you would have to reduce the amount of 80l to 7 ounces and raise the amount of liquid extract to 6 pounds, 12 ounces. Hope this helps.

__________________
Like my snazzy new avatar? Get Sons of Zymurgy swag, here, and brew with the best.

Revvy's one of the cool reverends. He has a Harley and a t-shirt that says on the back "If you can read this, the bitch was Raptured. - Madman

I gotta tell ya, just between us girls, that Revvy is HOT. Very tall, gorgeous grey hair and a terrific smile. He's very good looking in person, with a charismatic personality... he drives like a ****ing maniac! - YooperBrew